/**
 * Copyright (c) 2011-2023, James Zhan 詹波 (jfinal@126.com).
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.jfinal.template.ext.directive;

import java.util.Map;
import com.jfinal.kit.SyncWriteMap;
import com.jfinal.template.Directive;
import com.jfinal.template.EngineConfig;
import com.jfinal.template.Env;
import com.jfinal.template.TemplateException;
import com.jfinal.template.expr.ast.Assign;
import com.jfinal.template.expr.ast.ExprList;
import com.jfinal.template.io.Writer;
import com.jfinal.template.source.ISource;
import com.jfinal.template.stat.Ctrl;
import com.jfinal.template.stat.ParseException;
import com.jfinal.template.stat.Parser;
import com.jfinal.template.stat.Scope;
import com.jfinal.template.stat.ast.Define;
import com.jfinal.template.stat.ast.Include;
import com.jfinal.template.stat.ast.Stat;
import com.jfinal.template.stat.ast.StatList;

/**
 * #render 指令用于动态渲染子模板，作为 include 指令的补充
 * 
 * <pre>
 * 两种用法：
 * 1：只传入一个参数，参数可以是 String 常量，也可以是任意表达式
 *   #render("_hot.html")
 *   #render(subFile)
 *   
 * 2：传入任意多个参数，除第一个参数以外的所有参数必须是赋值表达式，用于实现参数传递功能
 *   #render("_hot.html", title = "热门新闻", list = newsList)
 *   
 *   上例中传递了 title、list 两个参数，可以代替父模板中的 #set 指令传参方式
 *   并且此方式传入的参数只在子模板作用域有效，不会污染父模板作用域
 *   
 *   这种传参方式有利于将子模板模块化，例如上例的调用改成如下的参数：
 *   #render("_hot.html", title = "热门项目", list = projectList)
 *   通过这种传参方式在子模板 _hot.html 之中，完全不需要修改对于 title 与 list
 *   这两个变量的处理代码，就实现了对 “热门项目” 数据的渲染
 *   
 * </pre>
 */
public class RenderDirective extends Directive {

    private String parentFileName;
    private Map<String, SubStat> subStatCache = new SyncWriteMap<String, SubStat>(16, 0.5F);

    public void setExprList(ExprList exprList) {
        int len = exprList.length();
        if (len == 0) {
            throw new ParseException("The parameter of #render directive can not be blank", location);
        }
        if (len > 1) {
            for (int i = 1; i < len; i++) {
                if (!(exprList.getExpr(i) instanceof Assign)) {
                    throw new ParseException("The " + (i + 1) + "th parameter of #render directive must be an assignment expression", location);
                }
            }
        }

        /**
         * 从 location 中获取父模板的 fileName，用于生成 subFileName
         * 如果是孙子模板，那么 parentFileName 为最顶层的模板，而非直接上层的模板
         */
        this.parentFileName = location.getTemplateFile();
        this.exprList = exprList;
    }

    /**
     * 对 exprList 进行求值，并将第一个表达式的值作为模板名称返回，
     * 开启 local assignment 保障 #render 指令参数表达式列表
     * 中的赋值表达式在当前 scope 中进行，有利于模块化
     */
    private Object evalAssignExpressionAndGetFileName(Scope scope) {
        Ctrl ctrl = scope.getCtrl();
        try {
            ctrl.setLocalAssignment();
            return exprList.evalExprList(scope)[0];
        } finally {
            ctrl.setWisdomAssignment();
        }
    }

    public void exec(Env env, Scope scope, Writer writer) {
        // 在 exprList.eval(scope) 之前创建，使赋值表达式在本作用域内进行
        scope = new Scope(scope);

        Object value = evalAssignExpressionAndGetFileName(scope);
        if (!(value instanceof String)) {
            throw new TemplateException("The parameter value of #render directive must be String", location);
        }

        String subFileName = Include.getSubFileName((String)value, parentFileName);
        SubStat subStat = subStatCache.get(subFileName);
        if (subStat == null) {
            subStat = parseSubStat(env, subFileName);
            subStatCache.put(subFileName, subStat);
        } else if (env.isDevMode()) {
            // subStat.env.isSourceListModified() 逻辑可以支持 #render 子模板中的 #include 过来的子模板在 devMode 下在修改后可被重加载
            if (subStat.source.isModified() || subStat.env.isSourceListModified()) {
                subStat = parseSubStat(env, subFileName);
                subStatCache.put(subFileName, subStat);
            }
        }

        subStat.exec(null, scope, writer);	// subStat.stat.exec(subStat.env, scope, writer);

        scope.getCtrl().setJumpNone();
    }

    private SubStat parseSubStat(Env env, String subFileName) {
        EngineConfig config = env.getEngineConfig();
        // FileSource subFileSource = new FileSource(config.getBaseTemplatePath(), subFileName, config.getEncoding());
        ISource subFileSource = config.getSourceFactory().getSource(config.getBaseTemplatePath(), subFileName, config.getEncoding());

        try {
            SubEnv subEnv = new SubEnv(env);
            StatList subStatList = new Parser(subEnv, subFileSource.getContent(), subFileName).parse();
            return new SubStat(subEnv, subStatList.getActualStat(), subFileSource);
        } catch (Exception e) {
            throw new ParseException(e.getMessage(), location, e);
        }
    }

    public static class SubStat extends Stat {
        public SubEnv env;
        public Stat stat;
        public ISource source;

        public SubStat(SubEnv env, Stat stat, ISource source) {
            this.env = env;
            this.stat = stat;
            this.source = source;
        }

        @Override
        public void exec(Env env, Scope scope, Writer writer) {
            stat.exec(this.env, scope, writer);
        }
    }

    /**
     * SubEnv 用于将子模板与父模板中的模板函数隔离开来，
     * 否则在子模板被修改并被重新解析时会再次添加子模板中的
     * 模板函数，从而抛出异常
     *
     * SubEnv 也可以使子模板中定义的模板函数不与上层产生冲突，
     * 有利于动态型模板渲染的模块化
     *
     * 注意： #render 子模板中定义的模板函数无法在父模板中调用
     */
    public static class SubEnv extends Env {
        public Env parentEnv;

        public SubEnv(Env parentEnv) {
            super(parentEnv.getEngineConfig());
            this.parentEnv = parentEnv;
        }

        /**
         * 接管父类 getFunction()，先从子模板中找模板函数，找不到再去父模板中找
         */
        @Override
        public Define getFunction(String functionName) {
            Define func = functionMap.get(functionName);
            return func != null ? func : parentEnv.getFunction(functionName);
        }
    }
}




